1. Field of the Invention
The present invention relates to a track count method for an optical disc in an optical disc system, and more particularly, to a track count method which generates track count signals based on generating a pseudo radio frequency zero crossing signal.
2. Description of the Prior Art
Before an optical pickup starts to read/record data from/to a compact disc or a digital versatile disc (DVD), it has to move to a target track of the compact disc or the DVD. When the optical pickup searches for the target track it crosses other tracks. The distance between the present location of the optical pickup and the target track can roughly be divided into two possible situations, short-term track crossing(short seek) and long-term track crossing(long seek). In both of these situations, the relative speed and direction between the optical pickup and the optical disc are important factors when an optical disc system controls the optical pickup to cross tracks. Only when the optical system has confirmed the moving direction of the optical pickup, can it accurately control asled motor to move the optical pickup to the target track so to read/record data from/to the optical disc. While the optical disc system controls the optical pickup to cross tracks, it constantly confirms the moving direction of the optical pickup.
Typical methods of confirming the moving direction of the optical pickup vary according to the speed of the optical pickup when it crosses tracks. When the moving speed of the optical pickup is slow, the optical disc system uses the optical pickup to emit light to a groove or a land of the optical disc for generating a reflected radio frequency ripple signal and a tracking error signal, which depends whether the light is reflected from the target track or not. A phase difference between the radio frequency ripple signal and the tracking error signal is used to determine the moving direction of the optical pickup. A DVD-RAM disc stores data on both grooves and lands to increase a capacity for data. Therefore, as shown in FIG. 1, a frequency of the radio frequency ripple(RFRP) signal of a data area is twice that of a blank area. This results in a substantial amount of noise, so that it is difficult to select a correct radio frequency zero crossing signal. As a result, the optical disc system cannot function well relying on the optical pickup, which cannot read the track cross signals accurately.